Method and device for an EGR-system and a valve as well as a regulation method and device

ABSTRACT

The invention is related to a method and a device for recirculation of a part of exhaust gases from an exhaust pipe ( 6, 9 ) of a diesel engine ( 1 ) to the inlet of the engine, the exhaust gases being diverted from the exhaust pipe ( 6, 9 ) and directed through a recirculation conduit ( 10 ) to a controllable valve device ( 12 ) arranged between the engine and the air intake ( 2 ) thereof for allowing supply of air/recirculated exhaust gases in a desired relation to the combustion chamber of the engine ( 1 ). The invention also relates to a particular valve having two controllable inlets, said valve being useful in the method or device according to the invention, and a regulation method and device for regulating the air/fuel relation of a diesel engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of co-pending U.S. appln. Ser.No. 09/831,435 filed Aug. 21, 2001 and which is a national phaseapplication under 35 U.S.C. §371 of International Appln. PCT/SE99/02029filed Nov. 9, 1999, the entire contents of both applications beingincorporated by reference herein.

The present invention is related to a method and a device for anEGR-system (Exhaust Gas Recirculation), particularly for use inheavy-duty diesel engines. The invention also relates to a valve whichis particularly suited for the method and device according to theinvention but the valve may also find use within other fields. Finally,the invention is also related to a regulation method and device for adiesel engine.

In order to reduce the contents of hazardous exhaust gases, particularlynitrogen oxide (NOx), so called EGR-systems are used since many years inmany types of combustion engines. Such systems admit a part of theexhaust gases to be recirculated to the intake system of the engine,where it is mixed with the intake air and is conveyed further to thecombustion chamber of the engine. The recirculated exhaust gases replacea part of the intake air and have a reducing effect on the formation ofNOx. A so called EGR-valve is then placed in connection with the exhaustsystem of the engine, the purpose of said valve being to regulate theamount of recirculated exhaust gases.

A method and a device according to the precharacterising parts ofenclosed claims 1 and 6 are disclosed in DE A1 4 007 516. Although thisprior art makes it possible to use an EGR-system in super charged dieselengines, where the pressure in the intake system downstream of the supercharger is higher than the pressure in a recirculation conduit from anEGR-valve some important disadvantages are inherent in this prior art.Thus, the valve device comprises separate dampers arranged in theEGR-recirculation channel and an air intake channel. Separate drivemotors are provided for these dampers, a fact which makes the valvedevice complicated and this also applies for a control device therefor.

OBJECT OF THE INVENTION

A primary object of the present invention is to provide a methodenabling a more reliable and simple regulation of the relationair/recirculated exhaust gases. As to the device according to theinvention, the aim is to simplify the valve device and provide for amore reliable and simple control thereof.

A secondary object of the invention is to provide a valve suitable formixing two fluids flowing through two inlet channels. Such a valveshould be suitable for general purposes but is particularly useful in anEGR-system for diesel engines, including super charged diesel engines.

A tertiary object of the invention is to provide a regulation method anddevice providing for improved regulation possibilities with regard to adiesel engine provided with an EGR-system.

SUMMARY OF THE INVENTION

The primary object of the invention is achieved by the features definedherein. The design of the valve device as comprising two dampers, whereat least one of the dampers always is open and where the other of thedampers is closable by means of a drive motor common to the dampersprovides for a simple design and a reliable operation.

The secondary object of the invention is achieved by means of the valveas defined herein.

The tertiary object of the invention is achieved by means of theregulation method and device as defined herein. Thus, this aspect of theinvention is based on use of probes and sensors connected to a controldevice for the valve device so as to enable regulation not only of therelation air/recirculated exhaust gases but also regulation of theair/fuel relation of the engine. This aspect of the invention providesfor an improved overall regulation of the engine and a smaller amount ofpollution.

Preferable developments of the basic aspects of the invention aredefined herein.

The use of an EGR-system as contemplated by the invention on an engineprovided with a catalyst and a particle filter according to the priorart results in a substantial reduction of the NOx contents. Thisreduction may be up to 50% and makes it possible to upgrade existingdiesel engines to present emission requirements and to upgrade moderndiesel engines to future emission requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by means of non-limiting embodimentsillustrated in the drawings, where

FIG. 1 illustrates a diagrammatical view of an EGR-system according tothe invention;

FIG. 2 a illustrates a sectioned valve according to the invention in oneend position;

FIG. 2 b is a section view of the valve in FIG. 2 a as viewed in thedirection of the arrow B—B;

FIG. 3 a illustrates a sectioned valve according to the invention in anintermediate position;

FIG. 3 b illustrates a section view of the valve in FIG. 3 a as viewedin the direction of the arrow B—B;

FIG. 4 a illustrates a cut valve according to the invention in a secondend position; and

FIG. 4 b illustrates a section view of the valve in FIG. 4 a as viewedin the direction of the arrow B—B.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a diagrammatical view showing the parts, which are essentialto the invention, of a combustion engine indicated with the referencecharacter 1. The engine is in the selected embodiment example a turbocharged diesel engine but as already mentioned the engine may be adiesel engine without super charging or a diesel engine with a differenttype of super charging than a turbo charger. Air is taken to the engine1 through an air intake, an air filter 2, and is directed via an inletair channel 3 to a turbo charger 4, where the air is super charged andthen conveyed further through an intercooler 5, where the super chargedair is cooled down before it is conveyed into the engine 1. The exhaustgases from the engine 1 are first directed through the second side ofthe turbo charger 4, namely that side which is the driving one, and thenthrough an exhaust pipe 6, a catalyst 7 and a particle trap 8 to finallybe emitted to the open air via an end pipe 9.

From the end pipe 9, i.e. an extension of the exhaust pipe after thecatalyst and particle trap, there is a branch, a recirculation conduit10, to recirculate from the exhaust gases a part thereof to the engine.The recirculation conduit 10 passes suitably through a cooler 11 to cooldown the recirculated exhaust gases and it connects to the inlet airchannel 3 via a valve device 12 controllable by means of an EGR controldevice 13. The valve device 12 may, with the assistance of the EGRcontrol device 13, regulate the relation between the supplied amount offresh air from the inlet air channel 3 and the supplied amount ofrecirculated exhaust gases from the recirculation conduit 10.

The EGR control device 13 regulating the valve device 12 is suppliedwith information about the actual operational state of the engine froma.o. a Lambda probe 14, a sensor 15 for the number of revolutions of theengine and a sensor 16 for engine load and this control device isprogrammed to control the valve device 12 and, accordingly, the mixingrelation fresh air/exhaust gases for the purpose of minimising thecontents of hazardous substances leaving the end pipe 9 and beingemitted into the open air. The programming of the EGR control device 13occurs in a previously known manner with regard to the relations betweenthe different factors given hereinabove. As is well known, a Lambdaprobe provides an output signal varying with the oxygen contents of theexhaust gases. The engine load sensor 16 may for instance be a throttleposition sensor and/or a sensor sensing the amount of fuel injected tothe engine. Also other sensors than those mentioned may be added toachieve a refined regulation.

The valve device 12 may comprise separate valves in the inlet airchannel 3 and in the recirculation conduit 10, said valves then beingseparately controllable by the EGR control device 13. Alternatively thevalve device 12 may also comprise a unit, in which flows from the inletair channel 3 and the recirculation conduit 10 may be selectivelybrought together, by means of valves contained in the valve device, to acommon output flow, which is conveyed further to the turbo charger forsuper charging and introduction into the engine via the intercooler 5. Aparticularly suitable valve device 12 in one unit is a particular partof the invention and will be described more closely hereunder.

The valve illustrated in FIGS. 2–4 is a type of mixing valve providingfor mixing of two in-flowing fluids in such a manner that the in-flowingfluid in one of the two inlet channels may be regulated from 0 tomaximum, and thereafter the in-flowing fluid in the second inlet channelfrom a maximum to 0.

In use of the valve according to the invention as illustrated in FIGS.2–4 as a valve device 12 in the method or device according to theinvention, the inlet air channel 3 is connected to the second inletchannel 18 of the valve, whereas the recirculation conduit 10 isconnected to the first inlet channel 17 of the valve. Furthermore, thereis in the valve an outlet channel 19, which in the present embodimentconveys the gases mixed in the valve to the turbo charger 4. In bothinlet channels 17 and 18, there are dampers 20 and 21, which arepivotable between an open and a closed position by means of anadjustment motor 22, for instance a step motor, to open or close theinlet channels. The two dampers 20, 21 are placed on concentric axles23, 24, which are rotatable by means of the adjustment motor 22 and anactuation pin 25 driven by the motor, said actuation pin being capableof pivoting actuation arms 26, 27 connected to the axles 23 and 24respectively. The actuation arms 26, 27 are spring loaded by one or moresprings 28, 29 to a normal position, illustrated in FIG. 3, where bothdampers 20, 21 are held in a position such that the inlet channels 17,18 are open.

In the position illustrated in FIG. 2 a, b, which is a startingposition, the adjustment motor 22 has, by means of its actuation pin 25and by means of the actuation arm 26, rotated the damper 20 to a closedposition, and thus, the first inlet channel 17 connected to therecirculation conduit 10 is closed and no exhaust gases may berecirculated to the turbo charger and the engine.

The second actuation arm 27 is maintained in its normal position by thespring 29, which means that the damper 21 in the second inlet channel 18connected to the inlet air channel 3 is maintained in its normallyopened position and allows free flow of inlet air through the valve viathe outlet channel 19 to the turbo charger. The adjustment motor 22 iscontrolled by the EGR control device 13 to regulate the relation betweenfresh air via the inlet air channel 3 and recirculated exhaust gases viathe recirculation conduit 10. In the position with the damper 21 open,the adjustment motor 22 may rotate, by means of its actuation pin 25 andby means of the actuation arm 26, the damper 20 from the entirely closedposition shown in FIG. 2 a, b to the position which is shown in FIG. 3a, b where also the damper 20 is in such a position that also the firstinlet channel 17 is open. The adjustment motor may also adjust thedamper 20 into any position between these two end positions.

The position illustrated in FIG. 3 a, b, which is the normal positionfor the adjustment motor 20, is such that the actuation pin 25 of theadjustment motor does not actuate any of the actuation arms 26, 27 butthey are maintained by the springs 28, 29 in a normal position, where,accordingly, the dampers 20, 21 open both inlet channels 17, 18.

FIG. 4 a, b illustrates a position contrary to the one in FIG. 2 a, b.Thus, the adjustment motor 22 has by means of its actuation pin 25 andby means of the actuation arm 27 rotated the damper 21 to a closedposition, which means that the connection of the inlet air channel 3with the outlet channel 19 is entirely interrupted whereas on thecontrary the first inlet channel 17 connected to the recirculationconduit 10 is entirely open and allows the recirculated exhaust gases tofreely flow further through the outlet channel 19 and then to the turbocharger 4 and further on to the engine. However, by means of theadjustment motor 22, the damper 21 may be adjusted into any intermediateposition between the end positions illustrated in FIGS. 3 and 4 to allowa desired amount, controlled by the EGR control device 13, of fresh airto be mixed with the recirculated exhaust gases.

Thus, with the valve according to the invention it becomes possible tocontrol, in a simple manner, a three-way valve having two inlets andhaving a normal position, where both inlets are open so that one or theother of the inlets may be controlled steplessly whereas the remaininginlet is maintained open. The valve may of course be controlled in othermanners than by means of the EGR control device 13 described above andit may be used in quite different connections than the one now describedand where corresponding control properties are desirable.

In a regulation method according to the invention, a control device isused which is supplied with information from a lambda probe 14, a motorspeed sensor 15 and an engine load sensor 16. The control device isconnected to a valve device, corresponding to the valve device 12described here-inabove, for regulation of the in-flowing amounts of airand/or recirculated exhaust gases to the engine. This valve device isarranged between the air filter and the inlet channel of the engine andmay, as also has been described for the valve device 12, compriseseparate valves in the inlet air channel and recirculation conduit, or athree-way valve of the kind also described hereinabove. The valve deviceis controllable in a corresponding manner as also described hereinabove,and the control device may therefore control, based on the input signalsreceived, the air/fuel relation of the engine by regulating the amountof in-flowing air and simultaneously regulating the relation between thesupplied fresh air and recirculated exhaust gases. This aspect of theinvention is applicable with or without supercharging.

With the regulation method and device according to the invention it ispossible to further decrease the NOx-contents in the exhaust gasesexiting from the end pipe of a diesel engine.

1. A method for recirculating a part of exhaust gases from an exhaustpipe (6,9) of a diesel engine (1) to an inlet of the engine, the exhaustgases being diverted from the exhaust pipe (6,9) and directed through arecirculation conduit (10) to a controllable valve device (12) arrangedbetween the engine and an air intake (2) thereof to enable supply ofair/recirculated exhaust gases in a desired relation to a combustionchamber of the engine, the valve device comprising dampers (20,21)arranged in inlet channels (17,18) for the recirculated exhaust gasesand air respectively, characterized in that at least one of the dampers(20,21) always is maintained open, the other damper (20,21) is closed bymeans of a drive motor (22) common to the dampers, and the drive motor(22) operates one of the dampers (20, 21) at a time and adjusts the sameinto any position between the open position and the closed position. 2.A method according to claim 1, characterized in that the exhaust gasesfrom the exhaust pipe (6,9) are diverted after a catalyst (7) and aparticle filter (8).
 3. A method according to claim 1, characterized inthat the relation air/recirculated exhaust gases is regulated by meansof a control device (13) controlling the valve device (12) based oninformation (14, 15, 16) supplied as to the actual operational state ofthe engine (1).
 4. A method according to claim 1, characterized in thatthe exhaust gases in the recirculation conduit (10) are cooled in acooler (11) arranged in the recirculation conduit (10).
 5. A methodaccording to claim 1, characterized in that in a super charged dieselengine the recirculated exhaust gases are supplied between the airintake (2) and a super charger (4).
 6. A device for recirculating a partof the exhaust gases from an exhaust pipe (6,9) of a diesel engine (1)to an inlet of the engine, a recirculation conduit (10) being providedfor diverting the exhaust gases from the exhaust pipe (6,9) anddirecting them to a controllable valve device (12) arranged between theengine and an air intake (2) thereof for enabling supply ofair/recirculated gases in a desired relation to a combustion chamber ofthe engine (1), the valve device comprising dampers (20,21) arranged ininlet channels (17,18) for the recirculated exhaust gases and airrespectively, characterized in that the valve device is arranged toalways maintain at least one of the dampers open, a drive motor (22)common to the dampers is arranged to close the other of the dampers(20,21) and the drive motor (22) is arranged to operate one of thedampers (20, 21) at a time and adjust the same into any position betweenthe open position and the closed position.
 7. A device according toclaim 6, characterized in that the drive motor (22) of the valve device(12) is controlled by a control device (13) regulating, by means of thepositions of the dampers (20,21), the relation air/recirculated exhaustgases in the valve device (12) based on information (14, 15, 16)supplied as to the actual operational state of the engine.
 8. A deviceaccording to claim 6, characterized in that the recirculation conduit(10) is connected to the exhaust pipe (6,9) of the engine after thecatalyst (7) and a particle filter (8).
 9. A device according to claim6, characterized by a cooler (11) arranged in the recirculation conduit(10) to cool the recirculated exhaust gases.
 10. A device according toclaim 6, characterized in that in a diesel engine having a supercharger, the valve (12) is arranged between the air intake (2) and thesuper charger.
 11. A device according to claim 6, characterized in thatthe drive motor is a step-motor (22) arranged to operate one of thedampers (20,21) at a time and adjust the same into an arbitraryposition.
 12. A device according to claim 6, characterized in that bothdampers (20,21) in a normal position are spring loaded (28,29) to anopen position.
 13. A device according to claim 6, characterized in thatthe valve device (12) comprises a first axle (23) on which a first one(20) of the dampers is arranged and a second axle (24) on which a secondone (21) of the dampers is arranged, the first and second axles (23,24)being concentric, and that both axles (23,24) are arranged to berotatable by the drive motor (22).
 14. A device according to claim 13,characterized in that the first axle (23) is connected to a firstactuation arm (26), that the second axle (24) is connected to a secondactuation arm (27) and the valve device (12) comprises an actuation pin(25) which is movable by means of the drive motor (22) in order torotate the first axle (23) and the second axle (24) by interaction withthe first actuation arm (26) and the second actuation arm (27),respectively, so as to control the position of the dampers (20,21). 15.A device according to claim 14, characterized in that the valve device(12) comprises springs (28,29) acting on the actuation arms (26,27) soas to spring load each damper (20,21) towards an open position.
 16. Avalve for mixing two fluids flowing through two inlet channels (17, 18),characterized in that dampers (20,21) are arranged in both inletchannels (17,18), at least one of the dampers always is open and that acommon motor (22) is arranged to close the other of said dampers(20,21), and the motor (22) is arranged to operate one of the dampers(20, 21) at a time and adjust the same into any position between theopen position and the closed position.
 17. A valve according to claim16, characterized in that the motor is a step-motor (22) arranged tooperate one of the dampers (20,21) at a time and adjust the same into anarbitrary position.
 18. A valve according to claim 17, characterized inthat both dampers (20,21) in a normal position are spring loaded (28,29)to an open position.
 19. A valve according to claim 17, characterized inthat the valve (12) comprises a first axle (23) on which a first one(20) of the dampers is arranged and a second axle (24) on which a secondone (21) of the dampers is arranged, the first and second axles (23,24)being concentric, and that both axles (23,24) are arranged to berotatable by the motor (22).
 20. A valve according to claim 19,characterized in that the first axle (23) is connected to a firstactuation arm (26), that the second axle (24) is connected to a secondactuation arm (27), and that the valve (12) comprises an actuation pin(25) which is moveable by means of the motor (22) in order to rotate thefirst axle (23) and the second axle (24) by interaction with the firstactuation arm (26) and the second actuation arm (27), respectively, soas to control the position of the dampers (20,21).
 21. A valve accordingto claim 20, characterized in that the valve (12) comprises springs(28,29) acting in the actuation arms (26,27) so as to spring load eachdamper (20,21) towards an open position.
 22. A method according to claim1, wherein a single drive motor (22) controls both dampers (20, 21)independently of one another.
 23. A method according to claim 22,comprising a common axle (23, 24) extending from said single drive motor(22) on which both said dampers (20, 21) are mounted.
 24. A methodaccording to claim 23, wherein said dampers (20, 21) are axiallydisplaced from one another along said common axle (23, 24) and situatedin said respective inlet channels (17, 18).
 25. A method according toclaim 1, wherein said dampers (20, 21) are linearly displaced from oneanother and situated in said respective inlet channels (17, 18)laterally situated with respect to one another.
 26. A device accordingto claim 6, wherein said single drive motor (22) controls both saiddampers (20, 21) independently of one another.
 27. A device according toclaim 26, comprising a common axle (23, 24) extending from said singledrive motor (22) on which both said dampers (20,21) are mounted.
 28. Adevice according to claim 27, wherein said dampers (20, 21) are axiallydisplaced from one another along said common axle (23, 24) and situatedin said respective inlet channels (17, 18).
 29. A device according toclaim 6, wherein said dampers (20, 21) are linearly displaced from oneanother and situated in said respective inlet channels (17, 18)laterally situated with respect to one another.
 30. A valve according toclaim 16, wherein said single drive motor (22) controls both saiddampers (20, 21) independently of one another.
 31. A valve according toclaim 30, comprising a common axle (23, 24) extending from said singledrive motor (22) on which both said dampers (20, 21) are mounted.
 32. Avalve according to claim 31, wherein said dampers (20, 21) are axiallydisplaced along said common axle (23, 24) extending from said singledrive motor (22) and situated in said respective inlet channels (17,18).
 33. A valve accordingly to claim 16, wherein said dampers arelinearly displaced from one another and situated in said respectiveinlet channels (17, 18) laterally situated with respect to one another.